Unsatisfied Link Error caused by attempting to load DLL twice

Question

Hi,
Hopefully someone can help me out with this issue.
My current situation is that I have an application which loads a Delphi based DLL when it loads. This application is in turn loaded from a seperate Java Application using reflection. The first time the application is opened it loads the DLL and works fine, however if I close the application and then re-open it i.e. create a new instance of the application, it crashes with
java.lang.UnsatisfiedLinkError: Native Library <filepath>\DataReader.dll already loaded in another classloader
I'm really not sure how to resolve this, I understand DLL's remain loaded until the VM terminates, but if I close the application and re-open it then I can't access the loaded version, or even test if it has been loaded. If anyone has any ideas about possible solutions, or where I should start looking for them I would apreciate it.
Many thanks

Answer 1

Ah, okay, this is probabbly me not being very clear, sorry. By application I was refering to a contained collection of Java Classes rather than an Application in the sense of a new OS Level Process. And I understand that when the Java VM Process ends the OS will unload the DLL's. Maybe my question should more be, how do I test if a particular instance of a DLL is already loaded?
Will try and explain a little bit better what the process is, in an attempt to figure out a solution. This all takes place within a single Java VM:
I have a Java "Application", lets call it A running on my system. The User clicks on a button in this application to load another "Application" (B).
A creates an instance of B using reflection, when an instance of B is created it loads a DLL into memory. This currently works fine.
The user then closes the instance of B.
The user then clicks the button in A again, A then creates a new instance of B using reflection. This new instance of B attempts to load the DLL into memory again.
This is the point where the crash occurs, with the "already loaded" error.
So, what I'm hoping someone could assist me with is how to determine if a DLL has already been loaded into memory. So far I've tried both setting a static flag when the DLL is loaded (the loading of the dll takes place inside a static constructor as recommended), and also tried
if (System.getProperty("MYDLL") == null)
               System.loadLibrary("MYDLL");
          }neither of which have proved effective. If anyone has any thoughts on what else I could try that would be appreciated.
Many thanks